PERSPECTIVES ON PERSPECTIVES ON LANDFILL GAS CAPTURE LANDFILL GAS CAPTURE

EFFICIENCYEFFICIENCY

Frank R. CaponiCIWMB – Climate Change Workshop

May 8, 2007WASTEWATER RECLAMATION

SOLID WASTE MANAGEMENT

WHAT IS LANDFILL GAS WHAT IS LANDFILL GAS CAPTURE EFFICIENCY?CAPTURE EFFICIENCY? Difficult to determine! Typical method:

Efficiency = Collection/Generation Gas collected = Measured Gas generated = Theoretical Model Gas surface emissions = Typically calculated Most estimation techniques incorrect!?? Ignores cover methane oxidation

COMMON SENSE APPROACHCOMMON SENSE APPROACHto Estimating Surface Emissionsto Estimating Surface Emissions

COMMON SENSE APPROACHCOMMON SENSE APPROACHto Estimating Surface Emissionsto Estimating Surface Emissions

COMMON SENSE APPROACHCOMMON SENSE APPROACHto Estimating Surface Emissionsto Estimating Surface Emissions

COMMON SENSE APPROACHCOMMON SENSE APPROACHto Estimating Surface Emissionsto Estimating Surface Emissions

COMMON SENSE APPROACHCOMMON SENSE APPROACHto Estimating Surface Emissionsto Estimating Surface Emissions

COMMON SENSE APPROACHCOMMON SENSE APPROACHto Estimating Surface Emissionsto Estimating Surface Emissions

COMMON SENSE APPROACHCOMMON SENSE APPROACHto Estimating Surface Emissionsto Estimating Surface Emissions

COMMON SENSE APPROACHCOMMON SENSE APPROACHto Estimating Surface Emissionsto Estimating Surface Emissions

COMMON SENSE APPROACHCOMMON SENSE APPROACH(verified through compliance monitoring)(verified through compliance monitoring)

COMMON SENSE APPROACHCOMMON SENSE APPROACHSummarySummary

Thriving vegetation indication of a well-controlled landfill– (we think >90 to 95% collection efficiency)

Surface concentration measurements of methane often at or near background– Regulations such as Federal NSPS or SCAQMD Rule

1150.1 require routine monitoring

Dead vegetation = composting– Air intrusion by to much vacuum– Federal NSPS limits oxygen at wells

COLLECTON EFFICENCYCOLLECTON EFFICENCYGeneration Modeling ApproachGeneration Modeling Approach Models developed by EPA or proprietary

variation Models developed as a compliance tool or

for state inventory development During development, EPA warned of

inaccuracies– Overpredicts by 40% to 2-3X

Consultants use to predict gas generation for energy projects

Often misused to calculate collection efficiency

COLLECTON EFFICENCYCOLLECTON EFFICENCYGeneration Modeling ApproachGeneration Modeling Approach

COLLECTON EFFICENCYCOLLECTON EFFICENCYGeneration Modeling ApproachGeneration Modeling Approach

COLLECTON EFFICENCYCOLLECTON EFFICENCYGeneration Modeling ApproachGeneration Modeling Approach

Excel File that could be easy to

operate

COLLECTON EFFICENCYCOLLECTON EFFICENCYGeneration Modeling ApproachGeneration Modeling Approach

COLLECTON EFFICENCYCOLLECTON EFFICENCYGeneration Modeling ApproachGeneration Modeling Approach

COLLECTON EFFICENCYCOLLECTON EFFICENCYGeneration Modeling ApproachGeneration Modeling Approach

MODEL PREDICTION

COLLECTON EFFICENCYCOLLECTON EFFICENCYGeneration Modeling ApproachGeneration Modeling Approach

COLLECTON EFFICENCYCOLLECTON EFFICENCYGeneration Modeling ApproachGeneration Modeling Approach

COLLECTION EFFICIENCY COLLECTION EFFICIENCY ESTIMATESESTIMATES

EPA uses 75% default– No basis

Some groups say 50% or less based on life cycle– Not applicable here- 94% waste in place

controlled Bogner field studies (flux chambers) show

85% or greater in Europe LACSD hybrid theoretical/measured show

95%+ Recent LACSD field study (flux chamber)

shows 100% (DTSC approved methods)

Flux Chamber Measurement Flux Chamber Measurement of Surface Emissionsof Surface Emissions

TOC as CHTOC as CH44 Distribution Distribution

Percent of 4 second readings > 4 ppmPercent of 4 second readings > 4 ppm

CAPTURE EFFICIENCYCAPTURE EFFICIENCYSmall Uncontrolled SitesSmall Uncontrolled Sites

ARB Early Action MeasureThese sites likely low quality methane– Sites may be older– Sites likely to be partially aerobic

Attempts to capture methane counterproductive– Placing site under vacuum will draw in more air– More air = less methane and composting– Managing low quality methane gas may need

supplemental fuel, such as natural gas to flare = more emissions of criteria pollutants

SUMMARYSUMMARY Landfills with Collection Systems well controlled Practical evidence such as healthy vegetation Theoretical models faulty – poor method of

estimating collection efficiency Field methods and hybrid methods more reliable

and accurate Data indicates collection efficiency 85% to 100%;

>95% likely Collecting landfill gas from small sites

counterproductive

Contact me with any Questions:

fcaponi@lacsd.org